virtio-net: switch to use new ctx API for small buffer

Use ctx API to store headroom for small buffers.
Following patches will retrieve this info and use it for XDP.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -410,7 +410,8 @@ static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
 static struct sk_buff *receive_small(struct net_device *dev,
 				     struct virtnet_info *vi,
 				     struct receive_queue *rq,
-				     void *buf, unsigned int len)
+				     void *buf, void *ctx,
+				     unsigned int len)
 {
 	struct sk_buff *skb;
 	struct bpf_prog *xdp_prog;
@@ -773,7 +774,7 @@ static int receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
 	else if (vi->big_packets)
 		skb = receive_big(dev, vi, rq, buf, len);
 	else
-		skb = receive_small(dev, vi, rq, buf, len);
+		skb = receive_small(dev, vi, rq, buf, ctx, len);
 
 	if (unlikely(!skb))
 		return 0;
@@ -806,12 +807,18 @@ static int receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
 	return 0;
 }
 
+/* Unlike mergeable buffers, all buffers are allocated to the
+ * same size, except for the headroom. For this reason we do
+ * not need to use  mergeable_len_to_ctx here - it is enough
+ * to store the headroom as the context ignoring the truesize.
+ */
 static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 			     gfp_t gfp)
 {
 	struct page_frag *alloc_frag = &rq->alloc_frag;
 	char *buf;
 	unsigned int xdp_headroom = virtnet_get_headroom(vi);
+	void *ctx = (void *)(unsigned long)xdp_headroom;
 	int len = vi->hdr_len + VIRTNET_RX_PAD + GOOD_PACKET_LEN + xdp_headroom;
 	int err;
 
@@ -825,7 +832,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 	alloc_frag->offset += len;
 	sg_init_one(rq->sg, buf + VIRTNET_RX_PAD + xdp_headroom,
 		    vi->hdr_len + GOOD_PACKET_LEN);
-	err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, buf, gfp);
+	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
 	if (err < 0)
 		put_page(virt_to_head_page(buf));
 
@@ -1034,7 +1041,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget)
 	void *buf;
 	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
 
-	if (vi->mergeable_rx_bufs) {
+	if (!vi->big_packets || vi->mergeable_rx_bufs) {
 		void *ctx;
 
 		while (received < budget &&
@@ -2202,7 +2209,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
 	names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);
 	if (!names)
 		goto err_names;
-	if (vi->mergeable_rx_bufs) {
+	if (!vi->big_packets || vi->mergeable_rx_bufs) {
 		ctx = kzalloc(total_vqs * sizeof(*ctx), GFP_KERNEL);
 		if (!ctx)
 			goto err_ctx;